深部单裂隙岩体结构面效应的三轴试验研究与力学分析

TRIAXIAL TEST RESEARCH AND MECHANICAL ANALYSIS BASED ON STRUCTURE SURFACE EFFECT OF DEEP ROCK MASS WITH SINGLE FISSURE

通过在类岩石材料中人工预制单裂隙,以常规三轴压缩试验为手段,研究深部单裂隙岩体的强度特征及破坏特性;用断裂力学原理分析单裂隙岩体沿结构面剪切破坏的影响因素,探讨裂隙岩体沿结构面滑动破坏的条件。研究结果表明:(1)单裂隙试样强度不仅具有明显围压效应,而且与裂隙倾角和尺寸关系密切;(2)裂隙是试件损伤的外在集中表现,裂隙试样的弹性模量和变形模量与围压、倾角及尺寸相关,裂隙尺寸对模量的影响最大,随着尺寸增加模量显著下降,而围压和倾角对模量的影响较轻微;(3)预制单裂隙试样的破坏形式既有沿结构面的滑动剪切破坏,也有试样自身的剪切破坏,而当裂隙尺寸较小时,还将产生裂隙重置后沿新结构面的剪切破坏;(4)单裂隙试样在理想II型剪切破坏时,断裂力学理论与莫尔库仑强度准则达到较好统一;(5)单裂隙试样沿结构面滑动破坏不仅取决于结构面倾角,而且与裂隙尺寸及围压大小关系密切,裂隙倾角适当,尺寸较小,围压较高时,试样才能产生沿结构面的滑动破坏,尺寸较大时,沿结构面滑动破坏对围压不敏感;(6)单裂隙三轴压缩试验中,既有I和II型裂纹产生,也有III型裂纹的扩展。研究成果能为含裂隙或断层的地下工程开挖、支护设计及其稳定性分析提供理论参考。

Through a single fissure is being artificially prefabricated into rock-like material, strength characteristics and failure modes of deep rock mass with single fissure are studied by means of conventional triaxial compression test. The impact factors and failure conditions of shear failure along discontinuities of fissured rock mass are also discussed based on the theory of fracture mechanics. The research results show that： （1） The strength of these samples is of great concern to confining pressure, fissure inclination angle and size. （2） Fracture is external concentrated expression of damage specimens. Deformation modulus and elastic modulus are related with confining pressure, fissure inclination angle and size which has great influence on modulus. It has a lower moduli of elasticity and deformation as fissure size increases： but confining pressure and fissure inclination angle have a slight effect on the moduli. （3） The failure modes of prefabricated single fissured samples can be classified into three types, i.e. shear failure across fissured plane, sample＇s own shear failure and shear failure across readjustment fissured plane when fissure size is small. （4） It has better consistency between fracture mechanics theory and the Mohr-Coulomb strength criterion if failure mode is an ideal II-type shear failure. （5） The shear failure of single fissured sample sliding across primary fissure plane depends on fissure inclination angle, size and confining pressure. Supposing fissure inclination is desired, the shear failure sliding across primary fissure plane will occur when fissure size is smaller but confining pressure is higher; and shear failure is not sensitive to confining pressure if fissure size is bigger. （6） I-type and II-type cracks of single fissured samples are found during triaxial compression test, and Ill-type cracks are also obtained. These conclusions can provide valuable theoretical reference for excavation, supporting design and stability analysis of underground engineering containing fissure and faults.